1. Field of the Invention
This application relates in general to machine vision systems and more particularly to a machine vision system with a detachable, dockable, backlight for enhancing the versatility of the inspection process.
2. Description of Related Art
It is often useful in machine vision systems, especially systems for inspecting objects to provide a backlight for illuminating the object from behind relative to the camera or imager (as used herein, camera includes both). Backlights permit features of the object, especially peripheral features, to be observed more clearly than when the object is directly illuminated. Such lighting is sometimes called profile lighting.
An example of an inspection system using a backlight is shown in U.S. Pat. No. 7,266,420. It is also useful in some applications to couple the backlight to the inspection camera so that the light and the camera move together when inspecting an object larger than the camera can image from a fixed location. The '420 patent accomplishes this by providing a large backlight and moving the camera. It is often desirable to provide a smaller backlight and move it with the camera. In cases where the object is supported between the backlight and the camera or in cases where the object is supported on a transparent deck with the light below the deck and the camera above it, this works well. However, there is a need for a machine vision system for inspecting objects that provides the option of direct illumination, back illumination, or both without the need for a transparent deck.
There is also a need for retrofitting existing coordinate measuring machines so that they can provide the function of video inspection systems. Coordinate measurement machines may have sensors such as contact probes that are movable in three dimensions to make measurements on an object under test. Such machines are frequently provided with massive tables for supporting the objects under test, often large granite tables. It is difficult to provide a profile light; that is, a light that illuminates the object-under-test from below, on such coordinate measuring machines. It has been contemplated to provide a complete transparent secondary or observation platform to support the article under test above the table and allow a profile light to move around underneath the article under test. Such platforms not only significantly increase the cost of upgrading the coordinate measuring machine to video inspection systems, but they compromise the load carrying capacity of the system.
There is a need for a method and apparatus for providing profile lighting in existing coordinate measuring machines that overcome these problems.